Abstract
Purpose
18F-8-cyclopentyl-3-(3-fluoropropyl)-1-propylxanthine (18F-CPFPX) is a potent radioligand to study human cerebral A1 adenosine receptors and their neuromodulatory and neuroprotective functions with positron emission tomography (PET). The purpose of this study was to determine the biodistribution and the radiation dose of 18F-CPFPX by whole-body scans in humans.
Methods
Six normal volunteers were examined with 12 whole-body PET scans from 1.5 min to 4.5 h after injection. Volumes of interest were defined over all visually identifiable organs, i.e. liver, gallbladder, kidneys, small intestines, heart, and brain to obtain the organs’ volumes and time-activity curves (TACs). TACs were fitted with exponential functions, extrapolated, multiplied with the physical decay and normalized to injected activities so that the residence times could be computed as area under the curve. Radiation doses were calculated using the OLINDA/EXM software for internal dose assessment in nuclear medicine.
Results
The liver uptake shows peak values (decay-corrected) of up to 35% of the injected radioactivity. About 30% is eliminated by bladder voiding. The highest radiation dose is received by the gallbladder (136.2 ± 66.1 μSv/MBq), followed by the liver (84.4 ± 10.6 μSv/MBq) and the urinary bladder (78.3 ± 7.1 μSv/MBq). The effective dose was 17.6 ± 0.5 μSv/MBq.
Conclusions
With 300 MBq of injected 18F-CPFPX a subject receives an effective dose (ICRP 60) of 5.3 mSv. Thus the effective dose of an 18F-CPFPX study is comparable to that of other 18F-labelled neuroreceptor ligands.
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Acknowledgements
The authors are thankful to Lutz Tellmann, Kornelia Frey and Elisabeth Theelen for excellent technical assistance. Johannes Ermert, Silke Grafmüller, Bettina Palm and Erika Wabbals are gratefully acknowledged for synthesis of 18F-CPFPX and Prof. Qaim for his help in preparing the manuscript.
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Herzog, H., Elmenhorst, D., Winz, O. et al. Biodistribution and radiation dosimetry of the A1 adenosine receptor ligand 18F-CPFPX determined from human whole-body PET. Eur J Nucl Med Mol Imaging 35, 1499–1506 (2008). https://doi.org/10.1007/s00259-008-0753-x
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DOI: https://doi.org/10.1007/s00259-008-0753-x